The present invention relates generally to bonding apparatus, and more particularly to novel bonding apparatus of the type enabling connection of a conductor wire to a conductive element on a work piece such as a microelectronic chip and the like.
In the design and manufacture of integrated circuit packages, such as employed in microprocessor devices, it is often desirable during the research and development stage to analyze or test the circuits on a semiconductor chip. The testing and analysis often entails conductive interconnection between two or more conductive elements on the semiconductor chip or alternatively, connecting a conductive element on the chip to an external circuit. The ability to conductively interconnect conductive elements within the boundary of a single semiconductor chip, alternatively termed a microelectronic chip, is desirable to facilitate development of new or alternate microcircuits without having to make an entirely new chip. Intraconnection of conductive elements within a single chip boundary also facilitates failure analysis of chips by enabling a bypass of a suspected defective area, thereby localizing the problem area.
Connection of circuits or conductive elements on semiconductor chips to each other or to external conductors, such as on a carrier board or lead frame, is conventionally accomplished by wire bonding. Wire bonding is basically a welding operation in which a weldment is formed between a conductive bonding wire or ribbon and a metallic conductive element or pad on the microelectronic chip or wafer. The weldment is formed when the two metal surfaces are brought into intimate molecular contact to enable short range interatomic attractive forces to become operative. This generally requires that both the conductive wire and the conductive element on the chip must experience some degree of plastic deformation in order to achieve a good bond.
The known wire bonder devices accomplish bonding generally in accordance with one of three basic techniques:
thermocompression ball bonding, which employs a flame or spark to melt the end of a conductor wire which forms a ball due to surface tension whereafter the ball is brought down onto a conductive element or pad on the chip and attached thereto by means of heat and pressure applied by the capillary tool through which the wire passes; thermosonic ball bonding, which is generally similar to thermocompression ball bonding except that ultrasonic energy is applied through the bonding tool and less heat is applied to the chip; and ultrasonic wedged bonding which employs a combination of pressure and ultrasonic energy applied by a wedge type bonding tool to produce a bond between the conductive wire and the conductive element on the chip.
The known wire bonders exhibit substantial drawbacks or limitations which significantly limit their application in microelectronic chip design and development, as well as use with chips having high circuit density which require very fine conductor wire in the bonding operation. For example, the known bonder devices do not readily lend themselves to use in making circuit interconnects within the boundaries of a single wafer or chip. Moreover, the known bonder devices do not facilitate use with high power microscopes having generally vertical sight lines such as are highly desirable with high density chips to reduce paralax.